"We mustn't forget that the shorelines these people would have lived on have gone."

As a rule of thumb, the North West is rising and the south east is sinking. The approxiamte axis of tilt is around the River Tees. Hence the raised beaches of Western Scotland and submerged sites such as Seahenge.
Of course isostatic effects and changing sea levels are a reality but what is also real is the fact that we do have some very well preserved coastal sites especially in the North west of Scotland.
Richards sampling took place from a number of locations both inland and coastal and the results from all contexts were unanimous.
In his 2003 article in Nature he states that
"these data are comparable with results obtained in Denmark, which also show a rapid dietry change in humans between the Mesolithic and Neolithic at about the same time"
I can't find a link to the Nature Article but If you would like to read it then drop me a line to my name at hotmail dot com.
As for the shorelines that "have gone", hopefully they haven't all gone forever. I just pray that salmon skin suits are waterproof, I would love to see one. I suppose they would be waterproof, you vary rarely hear a salmon complain of being wet.
cheers
fitz